Regulation and evolution of chlorophyll metabolism

Chlorophylls are the most abundant tetrapyrrole molecules essential for photosynthesis in photosynthetic organisms. After many years of intensive research, most of the genes encoding the enzymes for the pathway have been identified, and recently the underlying molecular mechanisms have been elucidated. These studies revealed that the regulation of chlorophyll metabolism includes all levels of control to allow a balanced metabolic flow in response to external and endogenous factors and to ensure adaptation to varying needs of chlorophyll during plant development. Furthermore, identification of biosynthetic genes from various organisms and genetic analysis of functions of identified genes enables us to predict the evolutionary scenario of chlorophyll metabolism. In this review, based on recent findings, we discuss the regulation and evolution of chlorophyll metabolism.     

Occurrence and abundance of bregmacerotid larvae in Kagoshima Bay,southern Japan,with descriptions of ontogenetic larval characters

Regular collections of ichthyoplankton were made with a larva net at 9–14 stations from Oct. 1983 to Dec. 1988 in Kagoshima Bay, totalling 817 collections from 66 cruises. A total of 2172 bregmacerotid larvae obtained from 195 collections of 33 cruises were identified asB. atlanticus (2001),B. neonectabanus (169),B. macclellandii (1) andB. nectabanus (1, tentative identification). The peaks of mean densities of larvae collected occurred in autumn forB. atlanticus andB. neonectabanus. The larvae ofB. atlanticus occurred throughout the bay, and their densities and frequency of occurrence were lower in the northern part of the bay. In the southern part of the bay, stations in its southwest quadrant showed higher densities than the others. The larvae ofB. neonectabanus occurred only in the southern part of the bay in which stations in the northwest quadrant showed higher densities than the others.     

Loading of lipophorin particles with phospholipids at the midgut of Rhodnius prolixus

³²P-Labelled midguts (³²P-midguts) of Rhodnius prolixus females were incubated in the presence of nonradioactive purified lipophorin and the release of radioactivity to the medium was analysed. The radioactivity found in the medium was associated with lipophorin phospholipids. When the ³²P-midguts were incubated in the absence of lipophorin, no ³²P-phospholipids were found in the medium. Comparative analysis by thin-layer chromatography of ³²P-phospholipids derived from metabolically labelled ³²P-midgut or lipophorin particles after incubation with ³²P-midgut showed some differences, revealing a possible selectivity in the process of phospholipids transfer. The transfer of phospholipids to lipophorin was linear with time up to 45 min, was saturable with respect to the concentration of lipophorin, and was half-maximal at about 5 mg/ml. The binding of ³²P-lipophorin to the midgut at O°C reached the equilibrium at about 1 h of incubation. The binding of ³²P-lipophorin was inhibited by an excess of nonradioactive lipophorin, which suggests a specific receptor for lipophorin. The capacity of midguts and fat bodies to transfer phospholipids to lipophorin varied during the days following the meal. When lipophorin enzymatically depleted of phospholipids by treatment with phospholipase A² was incubated with ³²P-midguts, the same amount of phospholipids was transferred, indicating a net gain of phospholipids by the particle. © 1995 Wiley-Liss, Inc.     

Ultrastructure of a Hexagonal Array in Exosporium of a Highly Sporogenic Mutant of Clostridium botulinum Type A Revealed by Electron Microscopy Using Optical Diffraction and Filtration

The ultrastructure of a hexagonal array in the exosporium from spores of a highly sporogenic mutant of Clostridium botulinum type A strain 190L was studied by electron microscopy of negatively stained exosporium fragments using optical diffraction and filtration. The exosporium was composed of three or more lamellae showing an equilateral, hexagonal periodicity. Images of the single exosporium layer from which the noise had been filtered optically revealed that the hexagonally arranged, morphological unit of the exosporium was composed of three globular subunits about 2.1 nm in diameter which were arranged at the vertices of an equilateral triangle with sides of about 2.4 nm. The morphological units were arranged with a spacing of about 4.5 nm. The adjacent globular subunits appeared to be interconnected by delicate linkers.     

Experimental Approach Reveals the Role of alx1 in the Evolution of the Echinoderm Larval Skeleton

Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms.     

Effects of different light intensities during the forenoon on the afternoon thermal sensation in mild cold

1. 1. The study aimed at knowing whether thermal sensation during afternoon cool exposure could be influenced by bright light (4000 lx) or dim light (200 lx) in the forenoon.

2. 2. The subjects felt cooler after exposure to dim light than to bright light.

3. 3. Melatonin in the urine was significantly higher in bright light than in dim light at 10:30 h and at noon.

     

Missing piece of top predator-based conservation: Demographic analysis of an owl population on a remote subtropical island

Top predators are frequently the target of conservation programs. Owls are such predators. However, previous studies of owls are biased to species occurring in temperate regions, whereas most owl species occur in tropical or subtropical regions and are understudied. Furthermore, owls are often endemic to islands and of unknown conservation status. Demographic data for such species are especially scarce although they are essential for initiating and promoting their conservation. As a case study of demographic analysis of owls in a tropical or subtropical area and on islands, we applied an integrated population model to 7-year monitoring data (2012–2018) of the Ryukyu Scops Owl population on Minami-daito Island, Japan. We used survival history data from 903 individuals, reproduction and sex ratio data from 213 broods, and count data of 2,526 individuals in total. Long-term averages of annual survival rates were 0.73 for adult females and 0.74 for adult males, although the sexual difference was not significant. Sex ratio estimates fluctuated annually and long-term averages were slightly skewed to males: 0.51 among fledglings, 0.54 among yearlings, and 0.52 among adults. Long-term averages of population size were estimated to be 273.4 females and 296.8 males. The long-term average of population growth rate was 0.98, suggesting a slightly declining trend. It was fortunate to recognize the declining trend during the early phase. Considering the general lack of fundamental ecological data on owls of tropical or subtropical areas and on islands, it seems likely that many endangered owl populations await conservation efforts.     

Stereoselective Synthesis of (S,E)-6-Isopropyl-3,9-dimethyl-5,8-decadienyl Acetate,the (S)-Enantiomer of the Yellow Scale Pheromone

The (S)-enantiomer of the sex pheromone of the yellow scale (Aonidiella citrina), (S,E)-6-isopropyl-3,9-dimethyl-5,8-decadienyl acetate, was stereoselectively synthesized from (R)-(+)-citronellic acid.     

Polyclonal Antibody Production in Murine Spleen Cells Induced by Staphylococcus

Polyclonal plaque-forming cell (PFC) responses in murine spleen cells induced by Staphylococcus aureus and S. epidermidis were studied. Injection of Balb/c mice with S. aureus strain 248βH resulted in the generation of anti-trinitrophenyl (TNP) and anti-sheep red blood cell PFC in their spleens. Cultures of Balb/c spleen cells in the presence of S. aureus 248βH, Cowan I, or a protein A-deficient mutant yielded many anti-TNP PFC. The larger the number of organisms that were added to the cultures, the better was the PFC response. Both living and killed organisms, were capable of inducing the response, but an excess of living 248βH organisms in the cultures abrogated the response. All of the organisms (12 strains of S. aureus and 11 strains of S. epidermidis) freshly isolated from patients had the ability to induce the polyclonal PFC response in cell cultures. These organisms stimulated cultured C3H/HeJ mouse spleen cells, which were unresponsive to bacterial lipopolysaccharide (LPS). Cultured cells from the spleens of athymic nu/nu mice also responded to these organisms, and the number of PFC in nu/nu cell cultures was always greater than that in nu/+ cells prepared from a haired litter mate. Moreover, the responses of nu/nu spleen cell cultures to which nylon wool column-filtered splenic nu/+ T cells were added were lower than expected. These findings suggest that the polyclonal PFC response to staphylococci is thymus independent, but that the magnitude of the response is regulated by mature T cells. Cultures of macrophage-depleted spleen cells responded to the organisms to an extent similar to that of the control. The 248βH organisms were less capable of stimulating spleen cells of 2-week-old mice (i.e., early maturing B cells) than LPS. However, spleen cells from adult (7-week-old) and aged (9-month-old) mice responded well to both the organisms and LPS. Previous sensitization with the organisms in vivo did not affect any polyclonal responses of spleen cells in vitro to either the organisms or LPS. The role of staphylococcal protein A in the polyclonal PFC response to staphylococci is discussed.